Propeller guard



April 1962 v. L. POLSON 3,027,864

PROPELLER GUARD Filed Nov. 14, 1960 INVENTOR. VJHGJL L. FOL-$0M BY HTfOIF/YA'Y United States Patent 3,027,864 PROPELLER GUARD Virgil L. Polson, 1175 El Centro Ave., Naps, Calif. Filed Nov. 14, 1960, Ser. No. 69,047 2 Claims. (Cl. 115-42) My present invention relates to propeller guards and more especially to a guard for an outboard motor propeller.

The primary object of the invention is the provision of a guard which when associated with the propeller of an outboard motor will protect the propeller against entanglement with weeds or the striking of obstructions when in operation in propelling a boat in the usual well known manner and in this way eliminate the possibility of damage to the propeller and adjuncts thereof.

Another object of the invention is the provision of a propeller guard, wherein the construction thereof in its entirety is novel, allowing easy fitting and removal at will and when fitted for association with the outboard motor propeller, it will furnish protection at opposite sides thereof by avoiding the striking of the blades against logs, rocks, or other obstructions that might come in contact with the propeller in the use of same on a boat.

A further object of the invention is the provision of a propeller guard which is simple in construction, thoroughly reliable and efficient in operation, strong, durable and inexpensive to manufacture and convenient for mounting and removal.

Another object of the invention is to provide a propeller guard which is so constructed that it will be supported and positioned at two fixed points upon the outboard motor and propeller assembly in such a way as to assure a maximum of strength in twisting obstructions and eliminating contact of the propeller blades with foreign objects when in operation, and which in addition to affording all of the above advantages will also provide a more complete guard for the propeller which will be found particularly effective in avoiding injury to surfboard and water-ski enthusiasts should they come in proximity with the propeller as in executing complicated maneuvers.

Other objects and advantages will be in part evident to those skilled in the art and in part pointed out hereinafter in connection with the accompanying drawing, wherein there is shown by way of illustration and not of limitation a preferred embodiment of the invention.

In the accompanying drawing:

FIGURE 1, is a side elevation of an outboard motor propeller showing the guard constructed in accordance with the invention applied thereto,

FIGURE 2, is a rear view of the guard as shown in FIGURE 1, with the propeller removed, and

FIGURE 3, is a front view thereof as applied to an outboard motor.

In the drawing, similar reference characters indicate corresponding parts throughout the several views.

As will be pointed out hereinafter, in addition to providing protection for the propeller of an outboard motor against damage due to snagging weeds or striking submerged or floating objects, it is also designed to provide effective protection against injury to persons such as surfboard and water ski enthusiasts who might accidentally find themselves in close proximity with the propeller of the boat to which the towline is attached. In its construction consideration has been given to the matter of turbulence such as might be set up in the water adjacent and forward of the propeller and in this respect the guard members and associated parts are streamlined and disposed in a manner that has been found to supplement the action of the cavitation plate generally provided on outboard "ice motors to provide for a more efficient functioning of the propeller.

As illustrated in the drawing and as a preferred construction my improved guard, except for a securing bolt and nut, is made as a single unitary structure which, as shown in the drawing, is adapted to be mounted upon the engine supporting housing of an outboard motor. As shown, it provides what might be termed a protective muzzle that encompasses the propeller, which in operation presents a dangerous condition, particularly where surfboat riders and water skiers are swimming in the area where the boat may be maneuvering. In addition to this, my guard has the further advantage that it will protect the motor propeller against damage due to contact with rocks as in shallow water or with logs or other floating debris which may be present along the line of travel of the boat.

In the accompanying drawing the numeral 10 designates the lower portion of the housing of a conventional out board motor which, as here shown, is provided with a fiat horizontally disposed undersurface 11 as a cavitation minimizing member. In this particular showing the housing carries an exhaust outlet 12 which directs the hot exhaust gases into the slipstream following a propeller 13. The housing construction 10 here shown is taken from one of the leading outboard motors now in the market and as shown it has a substantially elliptical downwardly extending portion 14 which connects at its lower end with a substantially cylindrical portion 15 in which the shaft for the propeller 13 is adapted and arranged to be driven by a vertical shaft, not shown, which extends downwardly from the engine through the elliptical portion 14 of the housing 10. At the underside of the cylindrical portion 15 of the housing there is a fin or keel 16 and at the outer end of the propeller shaft there is a nose cone 17 that operates to streamline the assembly and reduce turbulence in the wake of the boat.

Basically, my improved guard consists of a single unit having a breast or keel plate 20 to which there is welded or forged as an integral part seven ribs 21, 22, 23, and 24, the latter rib being formed as an extension to the breast or keel plate 20, whereas the other three ribs here shown are duplicated at the opposite side of the propeller 13. At its upper end the breast or keel plate is shown as having a housing encircling band 25 that is secured by a bolt and nut assembly 26 to the elliptical portion 14 of the housing 10. Extending downwardly at each side of the band 25 there is a bracket supporting portion 27, which as is more clearly shown in FIGURE 2 of the drawing is tolded upon itself to engage or clip over and center the breast or keel plate 20 upon the fin or keel 16 at the lower end of the housing. The lowermost rib 24 extends from the breast or keel plate 20 at a point immediately below the fin engaging sides of the bracket supporting member 27 and extends rearwardly to a point beyond the zone which the propeller operates.

In order to keep my improved guard as light as possible the ribs 21 to 24 are preferably constructed of spring steel and they are reduced to dimensions which, with due regard to their flexibility and strength requirements, will effectively serve their intended purpose. However, in order to reinforce these ribs and reduce the possibility of a flexing or bending of these ribs into the path of the blades of the propeller 13, I have provided the downwardly depending bracket supporting portions 27 at the sides of the housing with individual brackets 28, 29 and 30 which respectively act to space and maintain the ribs 21, 22 and 23 in their proper outwardly disposed radial positions with respect to the axis of the propeller 13. These brackets 28, 29 and 30 are in the form of flat fins which are of streamlined cross-section to reduce to a 3 any cavitation that might otherwise be established thereby.

While I have shown and described an outboard motor housing having a. particular construction, it will be understood that my invention may be modified to conform with such other structures as might be found in outboard motors of different manufacture, and having, for the sake of clearness'and in order 'to disclose my invention so that the same can be readily understood, described and illustrated a specific form and arrangement, I desire to have it understood that this invention is not limited to the specific form disclosed, but may be embodied'in other ways that will suggest themselves to persons skilled in the art. It is believed that this invention is new and all'such changes ascome within the scope of the appended claims are to be considered as part of this invention.

Having thus described my invention, what'l claim and desire to secure by Letters Patent is:

l. A guard for the propeller of an outboard motor having a depending motor drive shaft and a horizontal propeller shaft enclosing housing, comprising a keel plate having a housing encircling band at its upper end for securing same to the depending motor drive shaft housing as a keel forward of and extending under the zone in which a propeller operates, said housing encircling band having side members depending vertically along each side'of said horizontal propeller shaft enclosing housing and formed inwardly at their lower ends to engage and center "said keel plate at its lower end tosaid horizontal propeller shaft enclosing housing, a plurality of radially spaced rearwardly extending ribs secured at their forward ends to said keel plate and disposed in outwardly spaced relation about the horizontal propeller shaft enclosing housing,

i and radially extending bracing arms for each of said radiallyspaced ribs extending outwardly-from the" depending side members of said housing encircling hand, said bracing arms being streamlined and disposed edgewise to current flow, whereby cavitation is reduced to a in the zone in which said propeller operates.

2. A guard'for the propeller of an outboard motor having a depending drive shaft enclosing housing terminating in a substantially cylindrical hub for a horizontally disposed propeller shaft, comprising a keel plate having a housing encircling band at its upper end for securing it as a heel forward of and under the zone in which the propeller operates, said housing encircling band having vertically depending members on each side thereof contoured to encircle the cylindrical hub of said shaft supporting housing and being formed inwardly and connected together at their lower ends and secured to the keel plate at the underside ofsaid propeller shafit supporting housing, a plurality of r'earwardly extending radial spaced ribs secured at their forward ends to said keel plate and disposed'in outward radially spaced relation about the cylindrical hub of said shaft supporting housing, and a radially extending brace of streamline cross-section for each ofsaid radially spaced ribs extending outwardly from the contoured hub encirclingportion of said vertically depending members and disposed in planes radial to the axis of the propeller shaft, whereby cavitation will be avoided in the zone in which said propeller operates.

ReferencesCited in the file of this patent UNITED STATES PATENTS "2,597,551 Van Nort May 20, 1952 2,723,641 Taylor Nov. 15, 1955 

